In the fight against Ebola, both Sierra Leone and Liberia are deploying troops to control the spread of the disease. Soldiers have set up checkpoints and they've blockaded the areas hardest hit by the outbreak. In the meantime, experts are gathering at the World Health Organization in Geneva in search of new ways to stop the outbreak. Ebola is now confirmed in four countries but 90 percent of the new cases are in Liberia and Sierra Leone.

MELISSA BLOCK, HOST:

NPR's Ofeibea Quist-Arcton is in Freetown, Sierra Leone's capital. And Ofeibea, first talk about these new measures being taken to try to halt the spread of the virus, the troops that are now in the streets.

OFEIBEA QUIST-ARCTON, BYLINE: And they came in overnight so they've a bit of a surprise. What's happened is now troops and the police have blockaded the east of the country, and that's the epicenter of the Ebola outbreak here in Sierra Leone. So Kailahun and Kenema are effectively sealed off, and what the government is saying is that they've got to stop people from moving around. So people are effectively cut off, but the military do say they will allow food, medicines, essential services and of course those who are there to help - health workers, and others - aid workers into these zones that are now blockaded

BLOCK: And I believe Ofeibea it's a similar situation in Liberia where the president has declared a state of emergency. Combat troops are out blockading roads, trying to keep people from getting to the Liberian capital and spreading the disease.

QUIST-ARCTON: Indeed, so Monrovia is to be protected. Some people are saying whilst the western areas where again, again most of the Ebola - the epicenter of Liberia's Ebola crisis is happening - has been sealed off. But the military in both countries is saying this is the only way to go. Perhaps we have been a little bit laxed. We have been giving out education and awareness campaigns, telling people to stay where they are but people have been traveling up and down. This is the only way to restrict movements and they hope, to restrict the spread of Ebola in these two countries.

BLOCK: And how are people responding to these measures?

QUIST-ARCTON: Well, here in Sierra Leone for example, the National Health Workers Association president Joseph Tamba is saying you know, the state of emergency is necessary - everybody understands that now - but that people should've be given advance notice so that they could buy food, so that they could buy what they need. But the military here is saying look, we are going to allow all health workers, all aid workers to come and go, and we're going to allow services, food, medicines to be delivered, so don't worry. But it's a sort of thing that can panic people. And I suppose if you were just on a trip to Kenema or Kailahun suddenly you might be stuck there. How are you going to get back to your family wherever in the country? Same with Liberia. So people are nervous - they really are nervous about all to do with Ebola but I think everybody understands that because of the numbers, they have got to find a way to stop the spread.

BLOCK: Ofeibea there's also this development that there are now Ebola cases documented in Nigeria - it's Africa's most populous country - two deaths reported - at least half a dozen Ebola cases - that has to of huge concern.

QUIST-ARCTON: You know, Nigera - anywhere between 170 and 200 million people and the first person to die was in Lagos, the economic hug and the commercial capital. He came - a Liberian-American traveled from Liberia via Togo and Ghana to Lagos and died there. 21 million people in Lagos, and a nurse who was part of his medical care has also died. So there is you know, a red alert in Nigeria at the moment. And the health minister is saying he has been in touch with the Centers for Disease Control about looking into experimental drugs that have been used for the two Americans who tested positive for Ebola in Liberia and were medically evacuated home to the U.S. - is there any way that that can help other health workers in Africa who get sick, and of course other patients who suffer from Ebola? It's a huge debate now that starting on social media and elsewhere.